[2026] Python list vs tuple vs set | Mutability, Performance, and How to Choose

Introduction

“Isn’t list enough?” This guide compares list, tuple, and set so you can pick the right structure.

What you will learn

• Mutability and ordering
• Typical time costs
• Memory trade-offs
• A simple decision flow

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Table of contents

1. Quick comparison
2. Mutability
3. Performance
4. Memory
5. How to choose
6. Common mistakes
7. Advanced notes
8. Closing thoughts

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1. Quick comparison

	list	tuple	set
Mutable	Yes	No	Yes
Order	Yes	Yes	Not for logic (CPython preserves insertion order)
Duplicates	Allowed	Allowed	Unique
Index	O(1)	O(1)	No indexing
Membership	O(n)	O(n)	O(1) avg
Append/add	amortized O(1)	—	O(1) avg
Memory	Moderate	Lower	Higher (hash table)

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2. Mutability

아래 코드는 python를 사용한 구현 예제입니다. 코드를 직접 실행해보면서 동작을 확인해보세요.

lst = [1, 2, 3]
lst.append(4)
tup = (1, 2, 3)
# tup[0] = 10  # TypeError
s = {1, 2, 3}
s.add(4)
# s[0]  # TypeError — not subscriptable

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3. Performance

Membership: 아래 코드는 python를 사용한 구현 예제입니다. 코드를 직접 실행해보면서 동작을 확인해보세요.

n = 100000
lst = list(range(n))
s = set(range(n))
# 99999 in lst  # O(n)
# 99999 in s    # O(1) average — much faster at scale

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4. Memory

아래 코드는 python를 사용한 구현 예제입니다. 필요한 모듈을 import하고. 코드를 직접 실행해보면서 동작을 확인해보세요.

import sys
data = range(10000)
lst = list(data)
tup = tuple(data)
s = set(data)
# sys.getsizeof: tuple often < list << set for same elements

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5. How to choose

아래 코드는 mermaid를 사용한 구현 예제입니다. 각 부분의 역할을 이해하면서 코드를 살펴보시기 바랍니다.

graph TD
    A[Pick a structure] --> B{Order matters?}
    B -->|Yes| C{Need in-place edits?}
    B -->|No| D[set]
    C -->|Yes| E[list]
    C -->|No| F{Need as dict key?}
    F -->|Yes| G[tuple]
    F -->|No| H{Need fastest membership?}
    H -->|Yes| G
    H -->|No| E

Examples:

• General ordered collection → list
• Fixed point/color/config → tuple
• Dedup / fast membership → set
• Dict keys → tuple (immutable) not list

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6. Common mistakes

• Indexing a set
• Mutating a tuple in place (use new tuple)
• Using list as dict key

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7. Advanced

• Set algebra: |, &, -, ^
• namedtuple for readable tuples

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Closing thoughts

1. Order + mutation → list
2. Order + immutable → tuple
3. Uniqueness / fast contains → set
4. Measure if unsure
   Match structures to operations and your invariants.

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Related posts

• Python data structures
• Python performance
• Python collections

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Keywords

Python, list, tuple, set, data structures, time complexity, memory, comparison